16m E-MBS (Enhanced Multicast and Broadcast Service)
An E-MBS provides an efficient method for simultaneous transmission of common downlink data to a group of users who use a common multicast STID (MSTID) and FID. The E-MBS service is only provided in downlink and coordination or synchronization is performed between base stations belonging to one group in order to allow macro diversity.
E-MBS is associated with a service flow provided along with quality of service (QOS) and traffic parameters for the service flow. Service flows for transmitting E-MSB data are accounted for to an individual terminal participating in the service while the terminal performs a general operation. During accounting, the terminal conforms the service and learns parameters associated with the service flow.
Each base station which may provide an E-MBS service belongs to a specific E-MBS zone and one base station may belong to a plurality of E-MBS zones. The E-MBS zone is defined as one set of base stations using the same MSTID and FID in order to transmit content of a specific service flow. Each E-MBS zone is identified by a unique E-MBS zone ID.
In order to guarantee an appropriate multicast operation over a network of a base station supporting an E-MBS, MSTIDs and FIDs used for a common E-MBS content and service should be the same to all base stations included in the same E-MBS zone.
This allows a terminal which has already registered with a specific service to seamlessly receive an E-MBS in an E-MBS zone, without reregistering with another base station included in the E-MBS zone and performing uplink communication.
Hereinafter, a carrier will be briefly described.
A user may perform a modulation operation with respect to the amplitude, frequency and/or phase of a sine wave and a periodic pulse wave. A sine wave or a pulse wave for carrying information is called a carrier.
Examples of a carrier modulation scheme include a Single-Carrier Modulation (SCM) scheme and a Multicarrier Modulation (MCM) scheme. Among others, the SCM scheme is to perform modulation with respect to all information carried on one carrier.
The MCM scheme refers to a technology of dividing an overall bandwidth channel of one carrier into several sub-channels each having a small bandwidth and transmitting a plurality of narrowband sub-carriers through the sub-channels.
At this time, when the MCM scheme is used, each of the sub-channels is approximated so as to have a flat channel due to the small bandwidth. A user can compensate for distortion of a channel using a simple equalizer. In addition, the MCM scheme is implemented at a high speed using Fast Fourier Transform (FFT) and is more advantageous in high-speed data transmission than the SCM scheme.
As capabilities of a base station and/or a terminal have been developed, a frequency bandwidth provided or used by the base station and/or the terminal has expanded. Accordingly, in the embodiments of the present invention, a multicarrier system supporting a wideband by aggregating one or more carriers is disclosed.
That is, in the following multi-carrier system, one or more carriers are aggregated and used, unlike the MCM scheme of dividing one carrier into sub-carriers and utilizing the sub-carriers.
In order to efficiently use multiband or multicarrier, a technique of managing several carriers (e.g., several frequency carriers (FCs)) by one medium access control (MAC) entity has been proposed.
FIGS. 1(a) and 1(b) are diagrams illustrating a method of transmitting or receiving a signal based on a multiband radio frequency (RF).
In FIG. 1, in a transmitter and a receiver, one MAC layer may manage several carriers in order to efficiently use multicarrier. In order to efficiently transmit or receive multicarrier, it is assumed that both the transmitter and the receiver can transmit or receive multicarrier. Since the frequency carriers (FCs) managed by one MAC layer do not need to be contiguous to each other, flexible resource management is possible. That is, both contiguous aggregation and non-contiguous aggregation are possible.
In FIGS. 1(a) and 1(b), a physical layer (PHY) 0, a physical layer 1, . . . , a physical layer n−2 and a physical layer n−1 represent multiple bands of the present technique and each band may have an FC size assigned for a specific service according to a predetermined frequency policy. For example, the physical layer 0 (RF carrier 0) may have a frequency band size assigned for a general FM radio broadcast and the physical layer 1 (RF carrier 1) may have a frequency band size assigned for mobile telephone communication.
The frequency bands may have different frequency band sizes according to frequency band characteristics. However, in the following description, for convenience of description, it is assumed that each FC has a size of A [MHz]. Each frequency allocation band is representative of a carrier frequency for utilizing a baseband signal in each frequency band. Hereinafter, each frequency allocation band is referred to as “carrier frequency band” or simply “carrier” representative of each carrier frequency band if such use will not lead to confusion.
Recently, as in the 3GPP LTE-A, the above carrier may be referred to as “component carrier” in order to be distinguished from a subcarrier used in an MCM scheme.
Therefore, the above “multiband” scheme may be referred to as a “multicarrier” scheme or a “carrier aggregation” scheme.
FIGS. 2(a) and 2(b) show an example of using multicarrier in a general wireless communication system.
Multicarrier of a general technique may be a contiguous carrier aggregation as shown in FIG. 2(a) or a non-contiguous carrier aggregation as shown in FIG. 2(b). A unit for aggregating carriers is a basic bandwidth unit of a legacy system (e.g., LTE in case of a long term evolution (LTE)-advanced system or IEEE 802.16e in case of an IEEE 802.16m system) which is a general technique.
In the multicarrier environment of the general technique, the following two types of carriers are defined.
First, a first carrier (or a primary carrier) refers to a carrier for exchanging full physical (PHY)/MAC control information and traffic of a terminal and a base station. In addition, the primary carrier may be used for a general operation of a UE, such as network entry. Each terminal has one primary carrier in one cell.
A second carrier (or a secondary carrier) refers to a supplemental carrier which may be used to exchange traffic according to a rule and a BS-specific allocation command received from the first carrier. The second carrier may include control signaling in order to support a multicarrier operation.
In the general technique, the carrier of the multicarrier system may be divided into a fully configured carrier and a partially configured carrier based on the primary and secondary carriers.
The fully configured carrier refers to a carrier in which control signaling is set. In addition, parameters and information on multicarrier management and other carriers may be included in the control channels.
The partially configured carrier refers to a carrier in which all control channels supporting downlink transmission is set in a downlink carrier which is not paired with an uplink carrier in a time division duplex downlink transmission (TDD DL transmission) or frequency division duplex (FDD) mode.
In general, a terminal performs initial network entry through a primary carrier and may exchange information about mutual multicarrier capabilities in a registration process through exchange of a registration request/response (AAI_REG-REQ/RSP) message with a base station.